Electrostatic free electron laser

Abstract

An electrostatic free electron laser having an electromagnetic waveguide, means to produce a periodic longitudinal electrostatic field along the waveguide and an electron beam which passes through the waveguide. Radiative energy is generated by the laser as a result of the kinetic energy lost by the electron beam as it is decelerated during its interaction with the electromagnetic wave and the electrostatic field within the waveguide. In use as an oscillator, the electrostatic free electron laser includes a resonator either in addition to or instead of the waveguide.

I claim: 
     
       1. An electrostatic free electron laser comprising: a housing, said housing extending in a longitudinal direction, means located adjacent one end of said housing for producing an electron beam and directing said electron beam through said housing in said longitudinal direction, means located adjacent said one end of said housing for producing an electromagnetic wave of radiation and directing said electromagnetic wave through said housing in said longitudinal direction, and means extending in a direction transverse to said longitudinal direction along at least a portion of said housing for producing a periodic longitudinal electrostatic field within said housing whereby energy generated by said free electron laser is the result of the kinetic energy lost by said electron beam as it is decelerated during its interaction with said electromagnetic wave and said electrostatic field within said housing. 
     
     
       2. An electrostatic free electron laser as defined in claim 1 wherein said means for producing said periodic electrostatic field comprises a plurality of electrodes extending transversely along at least a portion of said longitudinally extending housing. 
     
     
       3. An electrostatic free electron laser as defined in claim 1 wherein said housing is an electromagnetic waveguide. 
     
     
       4. An electrostatic free electron laser as defined in claim 3 wherein said means for producing said periodic electrostatic field comprises a plurality of electrodes extending transversely along at least a portion of said longitudinally extending housing. 
     
     
       5. An electrostatic free electron laser as defined in claim 3 wherein said electromagnetic waveguide is a planar waveguide. 
     
     
       6. An electrostatic free electron laser as defined in claim 5 wherein at least a portion of said electromagnetic waveguide has a slightly curved configuration. 
     
     
       7. An electrostatic free electron laser as defined in claim 3 further comprising a resonator. 
     
     
       8. An electrostatic free electron laser as defined in claim 7 wherein said resonator is comprised of a pair of curved reflectors, said curved reflectors being positioned transverse to the direction of said electron beam. 
     
     
       9. An electrostatic free electron laser as defined in claim 1 further comprising means located adjacent at least a portion of said longitudinally extending housing to isolate said electrostatic field producing means from said electromagnetic wave. 
     
     
       10. An electrostatic free electron laser as defined in claim 9 wherein said isolating means is made up of a reflective material. 
     
     
       11. An electrostatic free electron laser as defined in claim 1 wherein said electron beam has a predetermined thickness, said thickness being substantially equal to the term β o  λ/[4π(1-β o  cos φ)], where λ is the wavelength of said electromagnetic wave, φ is the electromagnetic mode "zig-zag" angle and β o  =v o  /c where v o  is the velocity of said electron beam and c is the speed of light. 
     
     
       12. An electrostatic free electron laser as defined in claim 1 wherein said interaction of said electron beam and said electromagnetic wave is a coherent stimulated process produced by said periodic electrostatic field at a certain synchronism condition given by the equation β z  +2π/L=ω/v o  where β z  is the longitudinal component of the wave number of said electromagnetic wave, L is the period of said periodic electrostatic field, ω is the frequency of said electromagnetic wave and v o  is the velocity of said electron beam. 
     
     
       13. An electrostatic free electron laser as defined in claim 1 wherein said housing is formed of a cylindrical configuration. 
     
     
       14. An electrostatic free electron laser as defined in claim 13 wherein said periodic electrostatic field producing means comprises a plurality of transversely circumscribing electrodes having a ring-like configuration. 
     
     
       15. An electrostatic free electron laser as defined in claim 1 wherein said electron beam is of an annular cross-section. 
     
     
       16. An electrostatic free electron laser as defined in claim 1 wherein said housing is in the form of an open resonator. 
     
     
       17. An electrostatic free electron laser as defined in claim 16 wherein said resonator comprises a flat reflector and a curved reflector, said flat reflector and said curved reflector being positioned in opposed relationship to each other and both said reflectors lying substantially in planes along said longitudinal direction of said housing whereby said energy generated by said free electron laser is reflected off said reflectors in a direction transverse to the direction of said electron beam before being output through one of said reflectors.